Arrangement for color picture scanning

ABSTRACT

An arrangement for photoelectric scanning of color pictures evaluates scanning light beams in three or more color filters according to different sensitivity curves. Photoelectric receivers then derive evaluation signals which are coded in three color value signals. In such arrangements, construction which is as simple, as economical and as space saving as possible is desired. Linear charge transfer device image sensors are respectively aligned to one another and the same line of the color picture. The image points of at least one image sensor are divided into two or more groups to which color filters of different, group-specific evaluation curves and group-specific charge coupled devices are assigned at whose outputs separate evaluation signals occur. The area of application is in color film scanners in which a color television screen serves as the reproduction device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an arrangement for scanning a colorpicture in which color filters are provided which evaluate the lightbeams performing the scanning according to three or more sensitivitycurves lying in different spectrum areas and in which photoelectricreceivers are arranged behind the color filters to generate evaluationsignals individually allocated to these spectrum ranges.

2. Description of the Prior Art

An arrangement of the type generally set forth above can be derived fromthe book by H. Lang, "Farbmetrik und Farbfernsehen", Verlag R.Oldenbourg, Muenchen, 1978, pp. 122-124. In this publication, a linespot scanner for color transparencies is described in respect of FIG.7.6 in which a Braun tube having a luminescent point describing atelevision screen is provided as the light source. The light beams fromthe source and respectively focused on an image point of the colorpicture penetrate the picture and are divided into three light beams,evaluated by color filters according to various spectrum rangesensitivity curves, and photo currents are then produced in photomultipliers and converted into color value signals of the primary colorsred, green and blue. The color value signals then, for example, controlthe brightness of the primary colors of a color television picture tube.Such a control is illustrated in FIG. 5.2 on Page 89 of the Lang book.Because of the small amount of light made available to the photomultipliers, the signal-to-noise ratio is small in this arrangement.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an arrangement of thetype generally mentioned above, which is significantly more free ofinterference than the known arrangement.

This object is achieved, according to the present invention, byutilizing photoelectric receivers which consist of one or more linearcharge transfer device image sensors which are aligned with their imagepoint rows to one and the same line of the color picture and in that adevice for shifting the color picture projected onto the sensor planesis provided. The image points of at least one image sensor are combinedinto two or more groups, whereby they are respectively arranged behindcolor filters having different, group-specific spectrum ranges andwhereby they are connectible with one of the predetermined plurality ofgroup-specific charge transfer devices. The charge transfer devicesrespectively assigned to a group have an output for the sequentialread-out of all sensor signals derived from this group.

The advantage which can be achieved in practicing the present inventionis, in particular, that the arrangement for photoelectric color picturescanning can be constructed in a more simple and space-saving manner,whereby a particular interference-free operation is made possible at thesame time.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the invention, itsorganization, construction and operation will be best understood fromthe following detailed description, taken in conjunction with theaccompanying drawings, on which:

FIG. 1 is a diagrammatic view of a first exemplary embodiment of theinvention;

FIG. 2 illustrates, in planar form, a linear charge transfer deviceimage sensor;

FIG. 3 is a graphic illustration of the voltage-time waveforms forexplaining the manner of operation of an image sensor constructed inaccordance with FIG. 2;

FIG. 4 diagrammatically illustrates a second exemplary embodiment of theinvention;

FIG. 5 diagrammatrically illustrates a third exemplary embodiment of theinvention; and

FIG. 6 illustrates a further development of the charge transfer deviceimage sensor illustrated in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An arrangement for photoelectric scanning of a transparent color picture1 is illustrated in FIG. 1 as comprising a stationary light source 11, afirst optics 12, a second optics 13, a beam splitter 15, 15', colorfilters 21 and 22 and linear image sensors 4 and 4' assigned to thecolor filters 21 and 22. The image sensors 4, 4' are respectivelysituated in imaging planes on which a focused imaging of the colorpicture 1 occurs by means of the optics 12 and the optics 13.

The beam splitter 15, 15' divides the light beams emanating from thesource 11 and permeating the color picture 1 into two light beams B1 andB2 which are evaluated in the color filter 21 and the color filter 22and permit correspondingly filtered imagings to arise in the planes ofthe image sensors 4 and 4', respectively. As a beam splitter, forexample, a half-silvered mirror 15 may be employed along with acompletely reflecting mirror 15' placed opposite thereto. Each of thelinear image sensors has only one row of photosensitive points which arealso designed as image points. The image point row of the image sensor 4is designated 4a and that of the image sensor 4' is designated 4a'. Aline of the color picture 1, in the beam path illustrated in FIG. 1 theline proceeding through the point 16, which proceeds perpendicular tothe plane of projection is respectively imaged on the image point rows.

The color filter 21 evaluates the light beam B1 according to asensitivity curve which, for example, lies in a spectrum range assignedto the primary color green (G filter). On the other hand, the filter 21can also evaluate according to a sensitivity curve which lies in aspectrum range which, for example, embraces the entire range of visiblelight. Thereby, it then exhibits a range of maximum sensitivity in thespectrum range of the primary color green. In the latter case, one alsodesignates the color filter 21 as a W filter. The color filter 22consists of strip-like filter portions which are alternately assigned asR filters (red filters) and B filters (blue filters). Herewith, it isunderstood that the filter portions of the R type have a sensitivitycurve which lie in the spectrum range of the primary color red and thatthe filter portions of the B type have their sensitivity curve in thespectrum range of the primary color blue. A filter portion of the R typeand a filter portion of the B type are alternately placed in front ofthe image points of the image sensor 4' lying behind the filter 22within their row.

If the color filter 21 is designed as a G filter and the color filter 22consists of R and B filter portions, then an evaluation signal u_(G)occurs at the output 40A of the image sensor 4, whereas evaluationsignals u_(R) and u_(B) respectively appear at the outputs 40B' and 40C'of the image sensor 4'. These outputs correspond to the outputs 40A, 40Band 40C of FIG. 2 which will be discussed in detail below. Given a colorfilter 21 of the W type, an evaluation signal u_(W) can be obtained atthe output 40A.

Color value signals which then control the brightness of the primarycolors of a color television picture tube can be derived in a knownmanner from the evaluation signals u_(G), u_(R) and u_(B) or,respectively, from the evaluation signals u_(W), u_(R) and u_(B).Depending on the gradient of the sensitivity curves and upon the widthof the spectrum ranges defined thereby, a specific coding of theevaluation signals occurs in order to obtain the color value signals.Sensitivity curves of this type are illustrated, for example, in theaforementioned book by H. Lang on Page 91, FIG. 5.4.

FIG. 2 illustrates one of the two charge transfer device (CTD) imagesensors, for example, the sensor 4, as an integrated circuit on asemiconductor substrate, as viewed from the top. The semiconductorsubstrate consists, for example, of n conductive silicon and isreferenced 41. An electrically insulating layer of, for example, SiO₂covers the substrate surface and is designed significantly thinnerwithin the broken line 42 than outside of the broken line. One alsodesignates the thinner areas as gate oxide, and the thicker areas asfield oxide areas. A central electrode 43 is situated above theinsulating layer and is flanked on one side by electrode rows 44 and 45and on the other side by electrode rows 46 and 47. The electrodes areconductive structures which particularly consists of portions of anelectrically conductive coating applied over the entire surface. Thecoating, for example, is formed of polycrystalline, highly-dopedsilicon, or consists of a metal layer, for example, of aluminum. Themanufacture of the electrodes 43 and of the electrode rows 44-47 occursin a conventional manner, for example, by means of a series ofphotolithographic steps upon employment of masks which define thecontours of the individual structures.

More specifically, the locations of the semiconductor substrate 41covered by the electrode 43 and which are located beneath the thin oxideareas represent individual image points 48, 49, 50, 51, etc. of theimage sensor. Since these image points form a line, such an image sensoris designated as a linear image sensor. The electrode rows 44-47 arerespectively formed by individual electrodes 441, 442, 443, 444 . . .451, 452, 453, 454 . . . which lie closely adjacent one another.

The electrode 451 is located at the level of the image point 48, theelectrodes 452 and 461 are located at the level of the image point 49,the electrodes 441, 453 and 462 are located at the level of the imagepoint 50, the electrodes 442, 454, 463 and 471 are located at the levelof the image point 51, etc. A pair of transfer gate electrodes G₁ and G₂is provided and these electrodes are respectively located between theelectrode 43 and the electrode rows 45 and 46, and slightly overlap theelectrode rows 45 and 46, but are electrically insulated therefrom bymeans of an intermediate layer. Further transfer gate electrodes G₃ andG₄ are located between the electrode rows 44 and 45 and the electroderows 46 and 47. The electrode 43 is connected to a pulse voltage φ₁, andthe transfer gate electrodes G₁ -G₄ are connected to a pulse voltageφ_(G) by way of a common connection. Every fourth electrode 451, 454,etc. of the row 45 is connected with a pulse voltage φ.sub. 1 by way ofa common line; each fourth electrode 452, 455, etc. is connected to apulse voltage φ₂ by way of a common line; each fourth electrode 453,etc. is connected to a pulse voltage φ₃ ; and each fourth electrode 454,etc. is connected to a pulse voltage φ₄. In an analogous manner, theindividual electrodes of the row 46 are connected with the pulsevoltages φ₁ -φ₄, whereas the electrodes of the rows 44 and 47 areconnected with pulse voltages φ₁ '-φ₄ '. Each of the electrode rows44-47 belongs to a CCD and are pulsed by means of the pulse voltages φ₁-φ₄ or, respectively, φ₁ '-φ₄ '. At the lower end of each electrode row,electrodes 44g-47g are provided which are connected free of the clockpulse voltages but which, however, are connected to respective outputs44a-47a. These electrodes have output-side diffusion areas D1-D4arranged thereafter which are connected to a drain voltage U_(DD) by wayof a common connection 53. The outputs 44A-47A can be connected with acommon output 40A.

During operation, a pulse φ₁ is applied which determines the average orintegration time. Within the same, electric charges collect in the imagepoints 48-51, etc., under the influence of the illumination andcorresponding magnitude to the respective local illumination intensity.At the end of the integration time, a transfer gate pulse φ_(G) causesthe displacement of the charges out of the image points into the area ofthe charge transfer devices 44-47, in particular, the charge which aroseunder the electrode 48 under the electrode 451, the charge which goesunder the electrode 49 under the electrode 461, the charge which aroseunder the electrode 50 under the electrode 441, and the charge whicharose under the electrode 51 under the electrode 471. By means of theclock pulses φ₁ -φ₄ and φ₁ '-φ₄ ' temporally occurring according to FIG.3, the charges, after having passed through the charge transfer devices,are pushed through step-by-step under the electrodes 44g-47g and finallyarrive in the diffusion areas D1-D4. The potential displacementsoccurring at the electrodes 44g-47g are transmitted to the outputs44a-47a and produce read-out signals which consists of pulse-shapedportions occurring in succession, which respectively correspond to theillumination intensities in the image points successively read duringthe integration time.

The integration time defined by means of the next successive pulse φ_(I)coincides in time with the shift of the charges formed in the precedingintegration by way of the charge transfer devices 44-47.

An image sensor according to FIG. 2 is described in detail in the GermanPat. No. 2,553,658. A simplification of this circuit is possible insofaras the charge transfer devices 44 and 47 can be eliminated, whereby onereads only the devices 45 and 46. Thereby, the number of read imagepoints is respectively reduced to one-half, in particular, to the points48, 49 and such image points which respectively exhibit an interval withrespect to these which amounts to a multiple of four electrodeintervals. An image sensor simplification in this manner is described,for example, in the IBM Technical Disclosure Bulletin, Vol. 16, No. 1,June 1973, pp. 173-174. In place of the illustrated charge transferdevices 44-47 which are to be interpreted as SCCD devices with a chargetransport immediately beneath the substrate surface or as BCCD deviceswith a charge transport in the interior of the substrate, bucket brigadedevices (BBD) known per se can also be employed in the sense of thepresent invention. Both systems of charge transfer devices are describedin the book by Sequin and Tompsett, "Charge Transfer Devices", AcademicPress, New York, 1975, pp. 1-18.

Instead of charge transfer devices which operate in four-phaseoperation, charge transfer devices may be employed which, in a mannerknown per se, operate in two or three phase operation. Finally, thecenter electrode 43 in FIG. 3 can be dissected into an electrode rowcorresponding to the parts 44-47, whereby, first, a common pulse φ_(I)defining the integration time is supplied to all electrodes of this rowand, subsequently, clock pulses φ₁ -φ₄ corresponding to FIG. 3 arecommunicated to the individual electrodes. Thereby, however, one musttake into consideration that only the image points situated beneath eachfourth electrode are illuminated. In the latter case, the output 40A isthen connected to the lowest part of the electrode 43, which thenrepresents a "floating gate" electrode, whereby the charge transferdevice 44-47 can be omitted. In this case, the entire area of theinsulation layer lying under the electrode 43 is designed as a gateoxide area.

In FIG. 1, the image sensor 4' is likewise designed according to thisstructure disclosed in FIG. 2, whereby its outputs are referenced with40B' and 40C'.

For scanning the next line, the picture 1 in FIG. 1 is displacedparallel by one line interval, particularly in the framework of acontinuous forward feed motion. Thereby, the imagings of the picture 1projected onto the planes of the image sensors 4, 4' are also shifted,so that the image point rows are aligned to the next line. Thedisplacement can also be undertaken by means of the device whichtransports a multitude of color pictures which are applied onto a commoncarrier in the direction of the arrow. In particular, a color filmscanning can occur in this manner.

Another solution for achieving a line-wise forward feed resides in theprovision that a mirror 3 (FIG. 1) is arranged in the beam path of thelight beams, and which is rotatably mounted about a stationary axis 31.The beam is reflected by the mirror 3, which are again divided by meansof a light splitter 32, 32' into two light beams, displays the imagingsof the color picture 1 projected onto the planes of the two imagesensors 34, 35 in the direction of the double-headed arrows, as afunction of a rotary motion of the mirror 3.

In order to simplify the circuit set forth in FIG. 1, the chargetransfer devices 44 and 47 can be omitted in the sensor 4, and likewisein the sensor 4'.

FIG. 4 illustrates an exemplary embodiment of the invention in which adivision of the light beams, proceeding along the line 16 is omitted. Afilter 21' which has filter strips of the R, G and B types next to oneanother is inserted in the beam path. The image points of an imagesensor 4 lie in sequence behind the R, G and B filters. If one designsthe image sensor for a three-phase operation, which in FIG. 2 leads,among other things, to the fact that the charge transfer device 47 isomitted, then evaluation signals u_(B), u_(R) and u_(G) can be tapped atthe outputs 44A, 45A and 46A.

The arrangement according to FIG. 5 corresponds to that of FIG. 4 exceptfor the difference of the filter 21" which has filter strips of thetypes W, R, W, B, W, R, etc. lying next to one another. By doing so, afour-phase arrangement for the image sensor 4 designed in accordancewith FIG. 2 is provided, at whose outputs 46A, 47A and 40B (FIG. 2) theevaluation signals u_(R), u_(B) and u_(W) can be read.

FIG. 6 illustrates a further development of the image sensor illustratedin FIG. 2 in which the middle electrode 43 is longitudinally dividedinto two parts 43a and 43b which have a predetermined interval orspacing from one another. Thin oxide areas FD1, FD2, etc. illustrated inFIG. 2 and located between the parts 43a and 43b are re-doped so thatthe photo diodes arise which increase the sensitivity of the imagesensor. The portion of the thin oxide area illustrated in FIG. 2 whichrespectively lies next to such a photo diode, but lies beneath one ofthe two electrode portions 43a or 43b, then forms ametal-insulaton-semiconductor (MIS) capacitor which stores the chargecarriers generated by the photo diode.

For a better preparation of the evaluation signals read from the chargetransfer devices, it is expedient to post-connect sample and hold stageswhich store a read signal value until it is replaced by the nextsuccessive read signal value to the outputs 44a-47a or, respectively,the outputs 40b and 40c or 40a.

The color filters 21, 22, 21' 21" can either be arranged on transparentcarrier plates which are then secured to the image sensors or canconsist of color layers which are directly applied to the surface of theimage sensors.

In order to obtain the evaluation signals u_(R) and u_(B) it issufficient in many cases to select the plurality of assigned imagepoints significantly smaller than the plurality of image points requiredfor the derivation of the signal u_(W). For example, the plurality ofimage points serving for the production of the signals u_(R) and u_(W)can be respectively amount to one-fourth of the plurality of the imagepoints provided for the u_(W) signal.

Although I have described my invention by reference to particularillustrative embodiments thereof, many changes and modifications of theinvention may become apparent to those skilled in the art withoutdeparting from the spirit and scope of the invention. I therefore intendto include within the patent warranted hereon all such changes andmodifications as may reasonably and properly be included within thescope of my contribution to the art.

I claim:
 1. An arrangement for scanning a color picture with lightbeams, comprising:photoelectric receiving means including at least onecharge transfer device image sensor having a row of image pointsreceiving light from a line of the color picture, a plurality of chargetransfer devices operably connected to said image points; color filtermeans located in the light path including a plurality of color filterseach located in front of a respective image point, said plurality ofcolor filters being serially arranged with respect to one another in arow and having different spectrum ranges which repeat in a serialpattern so as to project a corresponding pattern of light on therespective image points; shift means for shifting the color images onsaid image points; said image sensor including output means forproviding sequential read-out of sensor signals.
 2. The arrangement ofclaim 1, comprising:means for shifting the light beam including apivotally-mounted mirror.
 3. The arrangement of claim 1, comprising:atransport device operable to shift the color picture perpendicular tothe line direction.
 4. The arrangement of claim 3, wherein:saidtransport device is constructed to include a common carrier for mountinga plurality of color pictures.
 5. The arrangement of claim 1, whereinsaid image sensor comprises:a doped semiconductor substrate includingphotodiodes in said substrate, and doped opposite thereto, as said imagepoints.
 6. The arrangement of claim 1, wherein said image sensorcomprises:a semiconductor substrate having a plurality ofmetal-insulation-semiconductor capacitors as said image points.
 7. Thearrangement of claim 6, comprising:a plurality of photo diodes eachadjacent a respective capacitor and forming therewith a respective imagepoint.
 8. The arrangement of claim 1, wherein:said color filter meanscomprises transparent carrier means and color filters mounted on saidcarrier means.
 9. The arrangement of claim 1, wherein:said color filtermeans comprises color filters mounted on said image sensor.
 10. Thearrangement of claim 1, comprising:a first charge transfer device imagesensor comprising at least two of said charge-transfer device imagesensors, said image points located in groups behind respective ones ofsaid color filters having different, group-specific spectrum ranges andoperably connected to with said at least two charge transfer devices;said at least two charge transfer devices having group-specific outputmeans; an additional charge transfer device image sensor comprisingadditional charge transfer devices connected to said shift means andhaving its own output, and an additional row of image points coupled tosaid additional charge transfer devices to receive light from the samepicture line of the color picture; and an additional color filter aheadof said additional charge transfer device image sensor and having adifferent spectrum range.
 11. The arrangement of claim 1, wherein:saidcolor filters comprise filter strips of first, second and third typeslocated in front of said image points in a predetermined sequence; eachof said color filter types having a different color sensitivity; theimage points associated with said filter strips of said first typeoperably connected to first ones of said charge transfer devices; theimage points associated with said filter strips of said second operablyconnected to second ones of said charge transfer devices; the imagepoints associated with said filter strips of said third type operablyconnected to third ones of said charge transfer devices; and said outputmeans comprises first, second and third outputs for said first, secondand third ones of said charge transfer devices.
 12. The arrangement ofclaim 11, wherein:said first, second and third types of color filterstrip cover the respective spectrum ranges of the primary colors green,blue and red; and said color filter strips are arranged in therepetitive sequence of first, second and third types.
 13. Thearrangement of claim 11, whereinsaid first type of color filter stripcovers approximately the entire spectrum range of visible light with asub-range of maximum sensitivity in the spectrum range of one of theprimary colors red, blue and green; said second and third types of colorfilter strips covering respective spectrum ranges of the two otherprimary colors; and said color filter strips arranged in the repetitivesequence of first type, second type, first type, third type, first type,second type, first type, third type, and so on.
 14. The arrangement ofclaim 13, wherein:said color filter strips of said first type having amaximum sensitivity in the sub-range of the primary color green.
 15. Thearrangement of claim 14, wherein:said first ones of said charge transferdevices are grouped into first and second charge transfer devices; firstimage points and second image points associated with said first type ofcolor filter strips operably connected to said first and second chargetransfer devices, respectively; and each of said first and second chargetransfer devices including a common output constituting said firstoutput.
 16. The arrangement of claim 15, and further comprising:aplurality of sample and hold circuits connected to respective first,second and third outputs.
 17. An arrangement for scanning a colorpicture with a scanning light beam scanning a line of a color picture,comprising:beam splitting means for splitting the scanning light beaminto first and second light beams; first color filter means located inthe path of said first light beam having a spectrum range whichapproximately covers the entire spectrum of visible light with asub-range of maximum sensitivity in the spectrum range of the colorgreen; second color filter means located in the path of said secondlight beam and comprising first and second filter parts arrangedalternately adjacent one another, said first filter parts having thesensitivity range of the primary color red and said second filter partshaving the sensitivity range of the primary color blue; shift means forproviding shift pulses; a first image sensor including first chargetransfer devices connected to said shift means and including a row offirst image points arranged in the path of said first light beam behindsaid first color filter means, and a first output for providing asequential read-out of signals corresponding to light sensed by saidimage points; and a second image sensor including second charge transferdevices and third charge transfer devices connected to said shift meansand including a row of second image points arranged in the path of saidsecond light beam behind said second color filter means and grouped infirst and second groups corresponding to said first and second colorfilter parts, said first group respectively operably connected to saidsecond charge transfer devices and said second group respectivelyoperably connected to said third charge transfer devices; said secondcharge transfer devices and said third charge devices includingrespective outputs for providing sequential read-out of signalscorresponding to light sensed by the row of second image points.
 18. Anarrangement for scanning a color picture with a scanning light beamscanning a line of a color picture, comprising:beam splitting means forsplitting the scanning light beam into first and second light beams;first color filter means located in the path of said first light beamhaving a spectrum range of the color green; second color filter meanslocated in the path of said second light beam and comprising first andsecond filter parts arranged alternately adjacent one another, saidfirst filter parts having the sensitivity range of the primary color redand said second filter parts having the sensitivity range of the primarycolor blue; shift means for providing shift pulses; a first image sensorincluding first charge transfer devices connected to said shift meansand including a row of first image points arranged in the path of saidfirst light beam behind said first color filter means, and a firstoutput for providing a sequential read-out of signals corresponding tolight sensed by said image points; and a second image sensor includingsecond charge transfer devices and third charge transfer devicesconnected to said shift means and including a row of second image pointsarranged in the path of said second light beam behind said second colorfilter means and grouped in first and second groups corresponding tosaid first and second color filter parts, said first group respectivelyoperably connected to said second charge transfer devices and saidsecond group respectively operably connected to said third chargetransfer devices; said second charge transfer devices and said thirdcharge devices including respective outputs for providing sequentialread-out of signals corresponding to light sensed by the row of secondimage points.